Eat your beans and drink your beer

by Yuko Naito

There is nothing better than thirst-quenching cold beer on hot summer evenings, and many Japanese would probably agree that one of the best snacks to match with beer is young green soybeans, known as edamame in Japanese.

Many people love edamame beans because they are inexpensive, tasty and easy to prepare — just boil the still green and soft bean pods for several minutes, drain and sprinkle with salt. Once you start popping the beans out of the pods into your mouth, you can hardly stop.

Edamame are practically unknown in the Western diet — they are seldom eaten even in the United States, the largest soybean producer in the world. Immature soybeans are a popular snack, however, in such Asian countries as Japan, China, Taiwan, Thailand and Vietnam.

Soybeans were introduced to Japan from China sometime between the 5th century B.C.E. and the 3rd century C.E. The habit of eating green soybeans is believed to have started in Japan. Old documents mention the eating of green soybeans starting either in the Nara or Heian periods (exactly when and why they ate them are unclear) and they became commonly consumed in the Edo Period.

It usually takes five months to harvest fully grown soybeans, but edamame are picked three months earlier, when the beans are still green and soft. According to edamame farmers, they have only three or four days when they can gather sweet and crispy beans. If they pick too early, the beans would be still too small, and if they miss the time by even one day, they would become too tough and the taste would be ruined.

While mature soybeans are classified in the nuts and beans group, edamame are categorized as green vegetables, and some research has shown that edamame beans combine the health benefits of legumes and green vegetables.

Regular soybeans are internationally known as a healthy, cholesterol-free food. Soybeans are rich in protein, iron, B vitamins, calcium, zinc and fiber. Several research projects have shown that regular consumption of soybeans and soy products can lower cholesterol levels and prevent heart disease. According to recent studies, soy also contains isoflavone, a substance that works like estrogen, helping to reduce symptoms in menopausal women and possibly reducing the chances of developing breast cancer.

Since edamame are, in effect, immature, the content of most nutrients is lower than that of mature soybeans. For instance, 100 grams of boiled edamame contain 11.4 grams of protein, while the same amount of boiled soybeans has 16 grams. The content of other valuable substances such as isoflavone and saponin is also 20-30 percent lower in edamame than in fully mature soybeans.

On the other hand, edamame beans have some benefits ordinary soybeans lack. For instance, still-green edamame contain vitamins A and C: 60 IU of vitamin A and 30 mg of vitamin C per 100 grams of fresh soybeans. Those vitamins are not found in mature soybeans, because they are consumed as antioxidants while the beans grow.

Unlike many green vegetables, edamame beans lose little vitamin C when boiled, because the edamame’s hard pods prevent the soluble vitamin from leaking into water, says Professor Yutaka Shinohara of Chiba University.

“Even so, you should not leave edamame beans in the water too long,” says Shinohara, “and the cooking time must be as short as possible to preserve the maximum amount of vitamin C. Some people trim the ends of pods before boiling, and this may cause some loss of vitamin C.”

A final benefit of edamame is to your digestion, especially when your system is enervated by summer heat.

“Soybeans contain trypsin inhibitor, a substance that impedes digestion,” says Ryoichi Masuda of the National Food Research Institute. “Undigested food stays in the bowels, and is fermented by coliform bacteria. This is why many Westerners complain they feel bloated after eating soybeans. You don’t have to worry about it with edamame, however, because they contain less of the inhibitor.”

The fresh edamame season is now almost over. Nowadays, however, you can enjoy the beans all year round, because frozen edamame are available at almost any supermarket. They are mostly imported from China and Taiwan, but the beans are frozen the day they are picked, so taste and nutrition suffer very little.

Some brands have been boiled before freezing and can be eaten after defrosting by microwave or rinsing under running water. Many cooking experts, however, recommend boiling them lightly anyway, saying you will find the taste as good as if they were fresh.